Sundial and nocturnal celestial timepiece



Jan. 8, 1952 THQMSQN 2,582,179

SUNDIAL AND NOCTURNAL CELESTIAL TIMEPIECE Filed May 26, 1949 2 SHEETS -SHEET l 3nvento1 I David Thorn-S n (Ittorneg 8, 1952 a I THOMSON 2,582,179

SUNDIAL AND NOCTURNAL CELESTIAL TIMEPIECE Filed May 26, 1949 2 SHEETS-SHEET 2 ISnbemor David Thbmson Patented Jan. 8, 1952 UNITED STATES PATENT-OFFICE SUNDIAL AND NOCTURNAL CELESTIAL TIMEPIECE David Thomson, Flint, Mich. Application May26, 1949, SerialNo. 95,431

(01. ss -s1) 2 Claims.

dial to be readily adjusted to accurately function at any selected geographical latitude.

Another object is to adapt'the gnomon of a sundial and its angularly graduated dial plate to be angularly adjusted in unison to assure sub stantial parallelism of the indicating edge of the gnomon with the earths axis of rotation.

Another objectis to accurately adapta sundial by a quite simple adjustment to different time systems, such a eastern, central, mountain, or Pacific standard time, Greenwich mean solar time, and the like.

Another object is to adapt a sundial, installed at any point of known latitude and longitude, to readily indicate, in addition to the time prevailing at that location, the corresponding time at any other point on the earths surface; of known longitude.

Another object is to adapt a sundialfor use in a nocturnal determination of time, entailing a certain observation of thestars.

Another object is to equip a sundial with two concentric rotativelyadjustable rings, one having'a' circle of graduations representing twentyfour hours andfractions thereof, and the other or calendar ring having a circle of graduations representing'the' months, days, and any desired lesser units of a year, the first-mentioned ring "being correlated with a gnomon to receive a timeindicating shadow cast by the sun, and being further correlated and coaxial with the calendar ring to afford computation of nocturnal time in conjunction with a stellar observation.

These and various other objects are attained by the construction hereinafter described and illustrated in the accompanying drawing, wherein:

Fig. 1 is a front elevational view of my improved sundial and celestial timepiece, including a fragmentary sectional showing.

Fig. 2 is. a side elevational view thereof.

Fig; 3 is a radial sectional view cf the dial rings of the instrument and their holder, taken on the line 3-3of Fig. 1.

Fig. 4 is an enlarged front view of. the dial rings, exemplifying an adjustment thereof suited to a nocturnal time reading.

Fig. 5 is a view of one of said dialrings, showing a rotative shifting thereof from its'normal position serving for sundial use.

Constructi n In the drawings, the reference character i designatesan annular holder having parallel front and rear faces and formed on its front face with acircular rib 2 midway between the margins of such face. Seated against said front face and separated by the rib 2 are inner and outer rings 3 and 4, having their front faces in a mutually flush relation and preferably also I'iush with said rib. Thering 3 preferably hasitsinnerperiphery flush with that of the holder I and theouter periphery of. the ring 4 is preferably flush with that of the. holder. The two rings are independently rotatively adjustable on the holder, being respectively held in selective adjustment by radial set screws 5 andjli, terminally abutting.

the rib 2. The rings has itsfront face angularly graduated to represent by 15 degree sectors the twenty-four hour divisions of a day, and any desired smaller time. units may be further indi-- cated. In numbering such graduations, it is preferred. to provide two semi-circular series each extending from 0 to 12. The ring 4 is graduated on a basis that 360 degrees. represents a year, such ring being divided into units representing, in their proper succession, the twelve calendar months, such units differing in arcuate extent according to varying time extent of the months. The rear face of the holder i is formed with opposed offsets E reducing thickness of the upper half of the holder, fora reason hereinafter explained. A gnomon B,.formed. preferablyby a sheet metal plate, is rigidly mounted on the holder i within itsc'entral circular aperture, such platehaving an upper edgeda coincident with the common axis of the holder l and rings 3 ands. The gnomon is proportioned to project at its edge in; materially forwardly andrearwardly beyond. the holder, the requisite rearward extent being, however, materially less than that in a. forward direction. The illustrated securing means forth'e gnomon is a pin 9 radially set into. the holder and bifurcated to straddle the gnomon, which may be welded to. such pin.

The described parts form a unit which issupported bya bracket 10 of approximate U-shape', its upstanding arms ma oppositely engaging the outer periphery of the holder. The upper ends of such arms carry a pair of. screws ll headed against the outer faces of the arms and threaded into diametrically opposed sockets of theholder.

Unthreaded portions, of said screws. are. fittedinthe arms Illa adapting the holder to pivot, such screws being normally tightened to clamp the holder between the arms and maintain it in a desired pivotal position. At least one side of the holder is marked with a scale l2 of degrees for accurately setting the holder at a desired inclination to the vertical. The bracket It may be held in its illustrated position in any desired manner, as by surmounting it on a pedestal I3 and anchoring it thereto by a headed screw M, or the like.

Sundial use of the instrument For accurate functioning of any sundial, the indicating edge of its gnomon must be parallel to the earth's axis of rotation. Moreover, if the graduated or dial face of such an instrument occupies a plane, it is essential that said indicating edge be normal to said plane, assuming that the graduations are uniformly spaced as is, of course, desirable. The described construction satisfies these requirements, first, by permanently installing the gnomon on the dial holder with the indicating edge So at the axis of the ring 3 which is to receive the shadowed projection of such edge. Pivotal adjustment of the unit comprising the holder and said ring about the axis established by the screws l i, permits compensation for any geographical latitude, assuming such axis to be first disposed transversely to the meridian intersecting the point of installation. The latitude or at least approximate latitude, in degrees, of any point of installation may be readily ascertained, and it is necessary, in effecting compensation, only to tilt the holder unit until such latitude is indicated on the scale H2. The screws l l are then tightened to maintain this adjustment.

The provision for rotation of the ring 3 in holder I may be termed a longitude adjustment. Ordinarily, the zero point of the graduations of said ring lies directly beneath the gnomon, as in Fig. l, and the shadow of the edge 8a projected by the sun at some point on the lower half of the graduated surface accurately indicates time. If, at any given time, it is desired to know the time prevailing at some distant location differing in longitude from the location of installation, the ring 3 is rotated through an angle equal in degrees to the angle of longitude between the point of installation and said distant location, it being assumed that the longitude of both discussed locations are known. Since the hour units in which the ring 3 is graduated are each equal to degrees, a desired adjustment in degrees may be efiected with reasonable accuracy. If the distant location is east of the location of installation, the ring 3 will be shifted counterclockwise, and the adjustment will be clockwise if the distant location is westerly. Upon such an adjustment, the instrument will indicate time at the remote location, just as if it were installed at such location. Thus in Fig. 5, there is illustrated a position of the ring 3 suited to indicate time at a location thirty degrees west of the point of installation of the instrument. In thus ascertaining the time prevailing at a distant location, if the time system in effect at such location is known, compensation for longitude may be simplified. Thus, for example, if eastern standard time prevails at location of installation, and central standard time at discussed distant location, the time differential is one hour and the ring 3 requires clockwise adjustment to that extent.

Rotational adjustability of the ring 3 presents another advantage in permitting ready compen- 4 sation for temporary changes in a time system in effect at point of installation of the instrument. Thus in some communities fast and slow" time systems are used at dififerent seasons, clocks being set ahead an hour in changing to fast" time and set back an hour for slow time. Sundials now available are suited to accurately indicate time according to one system only, but a rotative adjustment of the ring 3 adapts my improved instrument to any such periodic or intervmittent change in a local time system.

The reduction in thickness of the upper half of the holder I reduces the likelihood of the graduations of the ring 3 being shadowed by the holder. Also such reduction facilitates the projection in certain positions of the sun, of a shadow on the inner periphery of the ring 3, cast by the rear portion of the edge 3a, whereby the intersection of such shadow with the graduated front face of said ring indicates time.

Use as a nocturnal celestial clock By virtue. of its calendar ring 4, the described instrument may serve to accurately determine nocturnal time, provided the stars are visible. In deriving this function, the ring 3 is first rotatively adjusted to a position such that the radius established by the zero mark of the scale on'such ring is substantially parallel to the line jointly determined by the North Star (Polaris) and the pointer stars (Alpha and Beta) of the group known as the big dipper. This positioning of the ring 3 is greatly facilitated by the gnomon, since the latter occupies the vertical plane jointly determined by the North Star and the point of installation of the instrument. The pivotal axis established by the screws It may also serve to facilitate and lend accuracy to the described adjustment since such axis permits such tilting of the holder as will align the pointer edge of the gnomon with the North Star. The observer now notes from a watch or clock the time at which the described observation is taken, and rotatively adjusts the ring 5 until the date of such observation, as indicated on the calendar scale, radially coincides with the indication of such time on the scale carried by the ring 3. Thus for example, if the observation is made at nine p. m. on date April 10, the ring 4 is rotated until such date on such ring radially coincides with the time, nine 1). m., on the ring 3. When thus set, the calendar ring is secured in position by its screw 6. Thereafter, the instrument will serve independently of watch or clock, to indicate nocturnal time with substantial accuracy, whenever the stars are visible for observation. Such determination of time involves, first, a rotative setting of the ring 3 to establish parallelism or a close approximation thereof between the radius established by the zero mark of said ring and the line jointly determined by the North Star and pointer stars aforementioned. The observer then notes on the calendar ring the indication of the date of observation, and the correct time may then be read on the ring 3 at its point radially Y coinciding with such date.

Theory of above described nocturnal use In the course of a day (24 hours), the earth rotates on its axis 1.00274 times. There exists a quite common belief that each revolution is effected in exactly 24 hours but such belief overlooks the effect of travel of the earth in its orbit around the sun. The orbital travel is reverse in its direction to rotation of the earth on its axis, and the joint effect of the two motionsis to induce one rotation in 24 hours relative to the sun and a fraction of a turn (.00274) in excess of 360 degrees of rotation about the axis.

The North Star is not intersected by the extended axis of the earths rotation but is sufficiently near such axis that no material error results from the assumption of an intersection, for my purpose of nocturnal time indication. Rotation of the earth creates the illusion of a rotation of various other stars about the North Star, this seeming travel being 1.00274 revolutions in 24 hours. It is preferred to use the pointer stars of the big dipper in observing the angular extent of this apparent travel, since such stars are most readily located.

If each revolution of the earth were effected in exactly twenty-four hours, the calendar ring 4 would be superfluous in ascertaining time by an observation of the stars. Under such supposition, it would be necessary only to rotatively adjust the ring 3, immediately following an observation of the stars, so that the radius corresponding to time of such observation (as noted by a watch or clock) would parallel the observed stellar radius from the North Star to the pointer stars Alpha and Beta. By maintaining such position of the ring 3 or reestablishing such position (after any other adjustment) the correct time would be indicated during any subsequent nocturnal period by simply finding a radius of the ring 3 paralleling said stellar radius at the desired time.

Since, however, the earths rotation exceeds one revolution in twenty-four hours, the aforesaid stellar radius does not, for any given position thereof, indicate a certain constant time each night, and the purpose of the calendar ring is to compensate for the variance in progressive advance of such stellar radius, with respect to our time system. The calendar ring may be considered as representing the path of the earth in its annular orbit, and by setting such ring so that the date of a stellar observation, as indicated on said ring coincides radially with the time of such observation, the necessary correction will be made for subsequent settings of the ring 3 based on similar stellar observations.

In explanation of the decimal fraction, .00274, hereinbefore mentioned, it is to be understood that this is equal to /365- What I claim is:

1. A combined sundial and celestial timepiece comprising a dial holder having front and rear faces and formed with a substantially central aperture intersecting said faces, a dial ring rotatively adjustable on the holder, substantially about the axis of said aperture and graduated in angular units of 15 degrees centered at said axis and representing hours, a calendar ring mounted on the holder coaxially with the dial ring and rotatively adjustable on the holder about said axis. and carrying angular graduations centered at said axis, and representing a year as 360 degrees, and comprising units representing the months of the year in an arcuate series, means for independently holding said rings in selective positions of their specified rotative adjustments, a gnomon fixedly carried by the holder and projecting into said aperture and having an edge substantially coinciding with said axis, and a support for the holder afiording it an angular adjustment for latitude correction about a substantially horizontal axis substantially transverse to the vertical plane determined by said edge of the gnomon, and means for securing the holder in selective positions of its specified adjustment.

2. In an instrument for computing time, a dial holder having front and rear faces and formed with a substantially central aperture intersecting said faces, a dial ring rotatively adjustable on said holder substantially about the axis of said aperture and graduated in angular units of 15 degrees, centered at said axis and representing hours, a calendar ring mounted on the holder coaxially-with the dial ring and rotatively adjustable on the holder about said axis, and carrying angular graduation centered at said axis and representing a year as 360 degrees, and comprising units representing the months of the year in an arcuate series, means for independently holding said rings in selective positions of their specified rotative adjustments, and an element fixedly carried by the holder and projecting into said aperture and having an edge substantially coinciding with said axis.

DAVID THOMSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 692,060 McCormick Jan. 28, 1902 699,450 Christensen May 6, 1902 825,319 Hewitt July 10, 1906 1,044,238 Pilkington Nov. 12, 1912 1,270,505 -Fields June 25, 1918 1,629,238 Terraz May 17, 1927 1,763,827 Stephen June 17, 1930 2,337,587 Brocky Dec. 28, 1943 FOREIGN PATENTS Number Country Date 607,597 Germany 1 Jan. 3, 1935 

